* Oil prices consolidate after two days of gains * Short-selling ban on financial stocks takes effect * Coming up: U.S. retail sales; University of Michigan confidence index (Recasts, adds fresh quotes, new prices, previous SINGAPORE) By Claire Milhench LONDON, Aug 12 (Reuters) - Oil slipped below $108 a barrel on Friday, reversing direction after two straight days of gains, as the dollar strengthened and concerns about oil demand in industrialised nations weighed on prices. Brent crude futures LCOc1 for September were down 33 cents to $107.69 a barrel by 0838 GMT, after having earlier traded down over a $1 to $106.86. U.S. crude oil CLc1 was down 60 cents to $85.12 a barrel after falling over a $1 to $84.02 earlier. In its third consecutive week of decline, the contract is set to fall 2.6 percent against a fall of 9 percent last week. Traders and analysts said that $1 swings were unexceptional given the levels of market volatility. The decline follows decent gains in previous days. Concerns about oil demand in OECD countries are weighing on markets following warnings from the International Energy Agency on Wednesday. It said that a 3 percent GDP growth scenario for 2012 would halve the base case 2012 oil demand growth to only 600,000 barrels per day .

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